This invention relates to a method and a device for the continuous forming of a mat of particle lignocellulosic material by depositing the material on a continuous forming web from a batching unit. The particle material can consist of chips or fibers for the manufacture of particle board or fiberboard, preferably of the type MDF (Medium Density Fiberboard).
The particle material in the form of wood chips or wood fibers manufactured in a desintegration plant is transported to a forming station, which comprises a batching unit for batching the material flow down on a continuous forming web, on which a mat of the particle material is formed. The mat is thereafter compressed in one or several presses, to which it is continuously transported by the forming web. The final pressing to a finished board takes place in a hot press.
In the board industry, a production plant for board is requested to be able to manufacture board of varying width in response to the specifications of the customer.
In conventional production plants different width are manufactured by first forming a mat on the forming web, thereafter compressing the mat and finally removing the edge strips by means of circular saws or mills. These edge strips are again desintegrated and then transported back to the batching system via pneumatic or other transporting means. This system usually is called xe2x80x9cmat-trimmingxe2x80x9d.
Mat-trimming has the disadvantage of high energy conumption, because it requires much energy for compressing, desintegration and transport. Furthermore, as a result of the staying-time of the particle material on the forming web and of the fact, that the material again must be desintegrated, the material has not the same quality as the main flow which is mixed at the re-circulation to the batching system. Another disadvantage is that at multi-layer forming, i.e. at forming stations where mats for board with special surface layers are manufactured, the fiber material intended for surface layers is mixed with fiber material intended for central layers at the recirculation to the batching system.
Further, according to U.S. Pat. No. 3,057,022 the width of the mat is adjusted by means of movable collecting devices on both sides of the forming web in the forming station. However, the collected material is returned to the material storage chamber by means of an extensive conveying system. Such system is complicated and the returned material will be mixed with new material which might be of different quality and result in uneven mat quality.
The present invention has the object to bring about a method and a device at board manufacture, where the board width can be adjusted in a simple manner and at the same time the afore-mentioned shortcomings are avoided. This is achieved according to the invention in that the intended board width is determined already at the forming of the mat in the outlet from the batching unit from where a partial amount of particle material is discharged and directly distributed and deposited as a layer in the mat. The characterizing features of the invention are apparent from the attached claims.